1. Field of the Invention
The present invention generally relates to air quality management by continuing emissions monitoring systems and more specifically relates to the real-time monitoring of gas pollutant emissions emitted from industrial facilities.
2. Related Art
The requirement for real-time monitoring of stack gas pollutants emitted from industrial facilities is now commonplace, and the physical approach is usually the installation of a conventional continuous emissions monitoring system (xe2x80x9cCEMSxe2x80x9d). Conventional CEMS are typically electro-mechanical devices made up of four main parts: (1) a sampling system; (2) a data analyzer; (3) a calibration system; and (4) a data logging and communications system.
A conventional sampling system typically consists of a data acquisition system (xe2x80x9cDASxe2x80x9d) having programmable logic controllers and computer hardware that executes various software utilities to provide data processing. The data analyzer typically consists of additional software utilities to provide data analysis and further processing. A conventional calibration system typically consists of elctro-mechanical sensors and calibrators and corresponding software utilities. Finally, a conventional data logging and communications system usually consists of a database for storing CEMS information and a remote terminal unit (xe2x80x9cRTUxe2x80x9d) for electronically transmitting data to a receiving station such as the local air pollution control authority.
There are two main drivers for conventional CEMS. Of these two, by far the most compelling is the need to demonstrate compliance with environmental legislation such as the Integrated Pollution Prevention and Control (xe2x80x9cIPPCxe2x80x9d). The second driving factor behind the development of CEMS is increased efficiency of the combustion systems associated with the industrial facility.
The CEMS industry needs improved systems and methods for capturing, processing, analyzing and providing emissions data to regulatory agencies. The present invention provides novel systems and methods to meet this need.
A data acquisition system is provided as part of a CEMS, whereby the DAS is designed to perform all computations and data manipulations necessary to accept digital data from CEMS and other types of sensory equipment and prepare mass emission summary data for output to a regulatory agency in the form required by the regulatory agency. Such mass emission summary data may be for oxides of nitrogen (xe2x80x9cNoxxe2x80x9d), carbon monoxide (xe2x80x9cCOxe2x80x9d), oxides of sulfur (xe2x80x9cSoxxe2x80x9d) or any other gaseous pollutant for which mass emissions information must be computed.
A single application of the program can accommodate one or more physical emitting devices such as an engine, boiler, turbine, furnace, or other. The additional physical devices (beyond the first) can be accommodated by multiple (e.g., sequential or parallel) instantiations of the system or a single instantiation adapted to communication with a plurality of devices.
Each physical device associated with the system correlates to an internal logical device (xe2x80x9cDAS devicexe2x80x9d). Any one DAS device can be associated with any one of the physical devices. For example, if an industrial facility has three CEMS, one monitoring a boiler, one monitoring an engine, and one monitornig a furnace, the first DAS device would be associated with the boiler, the second DAS device would be associated with the engine, and the third DAS device would be associated with the furnace. Other combinations are also acceptable.
In another type of application, the DAS can be used in a cogeneration facility. For example, such a facility might have two physical devices requiring CEMS, namely an engine and a duct burner. The engine can be, for example, a gas turbine (e.g., driving a chiller) with waste turbine-heat recovery used to generate electric power via a steam turbine and generator. When the amount of steam produced with waste heat is inadequate to accommodate the electric power demand (load), duct burners are available (physically located in the engine exhaust duct) to provide supplemental heat for production of steam.
In an installation where the duct burner exhaust pollutants are monitored separately from that of the engine, the DAS can be used in its simplest configuration, namely, the engine is represented by one DAS device and the duct burner by a second DAS device. In some installations, however, the duct burner exhaust is directly and immediately combined with the turbine exhaust, and there is no way to directly measure the composition of the duct burner exhaust. This may be because the burners are physically located inside the turbine exhaust duct or because the duct burner exhaust duct is not amenable to sampling. In this situation, there may be NOx and oxygen analyzers monitoring the exhaust directly downstream of the turbine (Location One Analyzers) and another pair of analyzers (Location Two Analyzers) monitoring the combined exhaust downstream of the duct burners (i.e., monitoring the combined duct burner and turbine exhausts).
Under some circumstances, there may be an additional level of complexity due to the need for a secondary stack. It may be necessary to divert the turbine exhaust to that secondary stack, the main stack being used for duct burner exhaust alone, both turbine and duct burner exhaust may go to the main stack during some part of the time when both are operating, the turbine alone may vent to the main stack (duct burner inoperative), or part of the turbine exhaust may be diverted to the secondary stack when the turbine alone provides more than enough heat for electric power generation. In this situation, information (device status signal) is provided at each sampling time to the internal DAS device by the physical system, regarding on-off status of the turbine and of the duct burner, and regarding where the turbine exhaust is being vented (i.e., the main or secondary stack).
In this situation where the duct burner exhaust cannot be directly monitored, regulatory requirements may make it unacceptable from a regulatory standpoint to mathematically separate the two exhausts in the raw data even where the inherent nature of the data themselves would allow it, or it may be physically impractical or impossible to correctly do so. In such cases, the DAS devices may be configured to analyze the combined exhaust of the engine and duct burners and compute the required mass emission rates. For example, the first DAS device may be assigned directly to the turbine, and it analyzes the exhaust of the turbine alone, whether that is directed to the main or secondary stack. The second DAS device applies only to the turbine when its exhaust is directed to the main stack. And a third DAS device can represent the main stack itself. Then, to obtain duct burner emissions, the second DAS device output (turbine only when directed to the main stack) is subtracted from the third DAS device output (turbine plus duct burners if operating), to result in the quantification of the mass emissions from the duct burners alone.